diff options
Diffstat (limited to 'gnuradio-core/src/lib/general')
| -rw-r--r-- | gnuradio-core/src/lib/general/Makefile.am | 5 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/general.i | 4 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/gr_cpm.cc | 214 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/gr_cpm.h | 80 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/gr_cpm.i | 40 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/qa_general.cc | 2 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/qa_gr_cpm.cc | 140 | ||||
| -rw-r--r-- | gnuradio-core/src/lib/general/qa_gr_cpm.h | 49 |
8 files changed, 533 insertions, 1 deletions
diff --git a/gnuradio-core/src/lib/general/Makefile.am b/gnuradio-core/src/lib/general/Makefile.am index f210cee39..fe545f98c 100644 --- a/gnuradio-core/src/lib/general/Makefile.am +++ b/gnuradio-core/src/lib/general/Makefile.am @@ -55,6 +55,7 @@ libgeneral_la_SOURCES = \ gr_copy.cc \ gr_count_bits.cc \ gr_cpfsk_bc.cc \ + gr_cpm.cc \ gr_ctcss_squelch_ff.cc \ gr_decode_ccsds_27_fb.cc \ gr_deinterleave.cc \ @@ -176,6 +177,7 @@ libgeneral_la_SOURCES = \ libgeneral_qa_la_SOURCES = \ qa_general.cc \ qa_gr_circular_file.cc \ + qa_gr_cpm.cc \ qa_gr_firdes.cc \ qa_gr_fxpt.cc \ qa_gr_fxpt_nco.cc \ @@ -203,6 +205,7 @@ grinclude_HEADERS = \ gr_copy.h \ gr_count_bits.h \ gr_cpfsk_bc.h \ + gr_cpm.h \ gr_ctcss_squelch_ff.h \ gr_decode_ccsds_27_fb.h \ gr_diff_decoder_bb.h \ @@ -340,6 +343,7 @@ grinclude_HEADERS = \ noinst_HEADERS = \ qa_general.h \ qa_gr_circular_file.h \ + qa_gr_cpm.h \ qa_gr_firdes.h \ qa_gr_fxpt.h \ qa_gr_fxpt_nco.h \ @@ -367,6 +371,7 @@ swiginclude_HEADERS = \ gr_conjugate_cc.i \ gr_copy.i \ gr_cpfsk_bc.i \ + gr_cpm.i \ gr_ctcss_squelch_ff.i \ gr_decode_ccsds_27_fb.i \ gr_diff_decoder_bb.i \ diff --git a/gnuradio-core/src/lib/general/general.i b/gnuradio-core/src/lib/general/general.i index f9adff3fa..e965eea64 100644 --- a/gnuradio-core/src/lib/general/general.i +++ b/gnuradio-core/src/lib/general/general.i @@ -1,6 +1,6 @@ /* -*- c++ -*- */ /* - * Copyright 2004,2005,2006,2007,2008,2009 Free Software Foundation, Inc. + * Copyright 2004,2005,2006,2007,2008,2009,2010 Free Software Foundation, Inc. * * This file is part of GNU Radio * @@ -137,6 +137,7 @@ #include <gr_annotator_alltoall.h> #include <gr_annotator_1to1.h> #include <gr_burst_tagger.h> +#include <gr_cpm.h> %} %include "gri_control_loop.i" @@ -254,3 +255,4 @@ %include "gr_annotator_alltoall.i" %include "gr_annotator_1to1.i" %include "gr_burst_tagger.i" +%include "gr_cpm.i" diff --git a/gnuradio-core/src/lib/general/gr_cpm.cc b/gnuradio-core/src/lib/general/gr_cpm.cc new file mode 100644 index 000000000..a00526b52 --- /dev/null +++ b/gnuradio-core/src/lib/general/gr_cpm.cc @@ -0,0 +1,214 @@ +/* -*- c++ -*- */ +/* + * Copyright 2010 Free Software Foundation, Inc. + * + * GNU Radio is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3, or (at your option) + * any later version. + * + * GNU Radio is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +// Calculate the taps for the CPM phase responses + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include <cmath> +#include <cfloat> +#include <gr_cpm.h> + +#ifndef M_TWOPI +# define M_TWOPI (2*M_PI) +#endif + +//! Normalised sinc function, sinc(x)=sin(pi*x)/pi*x +inline double +sinc(double x) +{ + if (x == 0) { + return 1.0; + } + + return sin(M_PI * x) / (M_PI * x); +} + + +//! Taps for L-RC CPM (Raised cosine of length L symbols) +std::vector<float> +generate_cpm_lrc_taps(unsigned samples_per_sym, unsigned L) +{ + std::vector<float> taps(samples_per_sym * L, 1.0/L/samples_per_sym); + for (unsigned i = 0; i < samples_per_sym * L; i++) { + taps[i] *= 1 - cos(M_TWOPI * i / L / samples_per_sym); + } + + return taps; +} + + +/*! Taps for L-SRC CPM (Spectral raised cosine of length L symbols). + * + * L-SRC has a time-continuous phase response function of + * + * g(t) = 1/LT * sinc(2t/LT) * cos(beta * 2pi t / LT) / (1 - (4beta / LT * t)^2) + * + * which is the Fourier transform of a cos-rolloff function with rolloff + * beta, and looks like a sinc-function, multiplied with a rolloff term. + * We return the main lobe of the sinc, i.e., everything between the + * zero crossings. + * The time-discrete IR is thus + * + * g(k) = 1/Ls * sinc(2k/Ls) * cos(beta * pi k / Ls) / (1 - (4beta / Ls * k)^2) + * where k = 0...Ls-1 + * and s = samples per symbol. + */ +std::vector<float> +generate_cpm_lsrc_taps(unsigned samples_per_sym, unsigned L, double beta) +{ + double Ls = (double) L * samples_per_sym; + std::vector<double> taps_d(L * samples_per_sym, 0.0); + std::vector<float> taps(L * samples_per_sym, 0.0); + + double sum = 0; + for (unsigned i = 0; i < samples_per_sym * L; i++) { + double k = i - Ls/2; // Causal to acausal + + taps_d[i] = 1.0 / Ls * sinc(2.0 * k / Ls); + + // For k = +/-Ls/4*beta, the rolloff term's cos-function becomes zero + // and the whole thing converges to PI/4 (to prove this, use de + // l'hopital's rule). + if (fabs(fabs(k) - Ls/4/beta) < 2*DBL_EPSILON) { + taps_d[i] *= M_PI_4; + } else { + double tmp = 4.0 * beta * k / Ls; + taps_d[i] *= cos(beta * M_TWOPI * k / Ls) / (1 - tmp * tmp); + } + sum += taps_d[i]; + } + for (unsigned i = 0; i < samples_per_sym * L; i++) { + taps[i] = (float) taps_d[i] / sum; + } + + return taps; +} + + +//! Taps for L-REC CPM (Rectangular pulse shape of length L symbols) +std::vector<float> +generate_cpm_lrec_taps(unsigned samples_per_sym, unsigned L) +{ + return std::vector<float>(samples_per_sym * L, 1.0/L/samples_per_sym); +} + + +//! Helper function for TFM +double tfm_g0(double k, double sps) +{ + if (fabs(k) < 2 * DBL_EPSILON) { + return 1.145393004159143; // 1 + pi^2/48 / sqrt(2) + } + + const double pi2_24 = 0.411233516712057; // pi^2/24 + double f = M_PI * k / sps; + return sinc(k/sps) - pi2_24 * (2 * sin(f) - 2*f*cos(f) - f*f*sin(f)) / (f*f*f); +} + + +//! Taps for TFM CPM (Tamed frequency modulation) +// +// See [2, Chapter 2.7.2]. +// +// [2]: Anderson, Aulin and Sundberg; Digital Phase Modulation +std::vector<float> +generate_cpm_tfm_taps(unsigned sps, unsigned L) +{ + unsigned causal_shift = sps * L / 2; + std::vector<double> taps_d(sps * L, 0.0); + std::vector<float> taps(sps * L, 0.0); + + double sum = 0; + for (unsigned i = 0; i < sps * L; i++) { + double k = (double)(((int)i) - ((int)causal_shift)); // Causal to acausal + + taps_d[i] = tfm_g0(k - sps, sps) + + 2 * tfm_g0(k, sps) + + tfm_g0(k + sps, sps); + sum += taps_d[i]; + } + for (unsigned i = 0; i < sps * L; i++) { + taps[i] = (float) taps_d[i] / sum; + } + + return taps; +} + + +//! Taps for Gaussian CPM. Phase response is truncated after \p L symbols. +// \p bt sets the 3dB-time-bandwidth product. +// +// Note: for h = 0.5, this is the phase response for GMSK. +// +// This C99-compatible formula for the taps is taken straight +// from [1, Chapter 9.2.3]. +// A version in Q-notation can be found in [2, Chapter 2.7.2]. +// +// [1]: Karl-Dirk Kammeyer; Nachrichtenübertragung, 4th Edition. +// [2]: Anderson, Aulin and Sundberg; Digital Phase Modulation +// +std::vector<float> +generate_cpm_gaussian_taps(unsigned samples_per_sym, unsigned L, double bt) +{ + double Ls = (double) L * samples_per_sym; + std::vector<double> taps_d(L * samples_per_sym, 0.0); + std::vector<float> taps(L * samples_per_sym, 0.0); + + // alpha = sqrt(2/ln(2)) * pi * BT + double alpha = 5.336446256636997 * bt; + for (unsigned i = 0; i < samples_per_sym * L; i++) { + double k = i - Ls/2; // Causal to acausal + taps_d[i] = (erf(alpha * (k / samples_per_sym + 0.5)) - + erf(alpha * (k / samples_per_sym - 0.5))) + * 0.5 / samples_per_sym; + taps[i] = (float) taps_d[i]; + } + + return taps; +} + + +std::vector<float> +gr_cpm::phase_response(cpm_type type, unsigned samples_per_sym, unsigned L, double beta) +{ + switch (type) { + case LRC: + return generate_cpm_lrc_taps(samples_per_sym, L); + + case LSRC: + return generate_cpm_lsrc_taps(samples_per_sym, L, beta); + + case LREC: + return generate_cpm_lrec_taps(samples_per_sym, L); + + case TFM: + return generate_cpm_tfm_taps(samples_per_sym, L); + + case GAUSSIAN: + return generate_cpm_gaussian_taps(samples_per_sym, L, beta); + + default: + return generate_cpm_lrec_taps(samples_per_sym, 1); + } +} + diff --git a/gnuradio-core/src/lib/general/gr_cpm.h b/gnuradio-core/src/lib/general/gr_cpm.h new file mode 100644 index 000000000..cae6fe313 --- /dev/null +++ b/gnuradio-core/src/lib/general/gr_cpm.h @@ -0,0 +1,80 @@ +/* -*- c++ -*- */ +/* + * Copyright 2010 Free Software Foundation, Inc. + * + * GNU Radio is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3, or (at your option) + * any later version. + * + * GNU Radio is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + + +#ifndef INCLUDED_GR_CPM_H +#define INCLUDED_GR_CPM_H + +#include <vector> + +class gr_cpm +{ + public: + enum cpm_type { + LRC, + LSRC, + LREC, + TFM, + GAUSSIAN, + GENERIC = 999 + }; + + /*! \brief Return the taps for an interpolating FIR filter (gr_interp_fir_filter_fff). + * + * These taps represent the phase response \f$g(k)\f$ for use in a CPM modulator, + * see also gr_cpmmod_bc. + * + * \param type The CPM type (Rectangular, Raised Cosine, Spectral Raised Cosine, + * Tamed FM or Gaussian). + * \param samples_per_sym Samples per symbol. + * \param L The length of the phase response in symbols. + * \param beta For Spectral Raised Cosine, this is the rolloff factor. For Gaussian + * phase responses, this the 3dB-time-bandwidth product. For all other + * cases, it is ignored. + * + * Output: returns a vector of length \a K = \p samples_per_sym x \p L. + * This can be used directly in an interpolating FIR filter such as + * gr_interp_fir_filter_fff with interpolation factor \p samples_per_sym. + * + * All phase responses are normalised s.t. \f$ \sum_{k=0}^{K-1} g(k) = 1\f$; this will cause + * a maximum phase change of \f$ h \cdot \pi\f$ between two symbols, where \a h is the + * modulation index. + * + * The following phase responses can be generated: + * - LREC: Rectangular phase response. + * - LRC: Raised cosine phase response, looks like 1 - cos(x). + * - LSRC: Spectral raised cosine. This requires a rolloff factor beta. + * The phase response is the Fourier transform of raised cosine + * function. + * - TFM: Tamed frequency modulation. This scheme minimizes phase change for + * rapidly varying input symbols. + * - GAUSSIAN: A Gaussian phase response. For a modulation index h = 1/2, this + * results in GMSK. + * + * A short description of all these phase responses can be found in [1]. + * + * [1]: Anderson, Aulin and Sundberg; Digital Phase Modulation + */ + static std::vector<float> + phase_response(cpm_type type, unsigned samples_per_sym, unsigned L, double beta=0.3); +}; + +#endif /* INCLUDED_GR_CPM_H */ + diff --git a/gnuradio-core/src/lib/general/gr_cpm.i b/gnuradio-core/src/lib/general/gr_cpm.i new file mode 100644 index 000000000..f01aba34e --- /dev/null +++ b/gnuradio-core/src/lib/general/gr_cpm.i @@ -0,0 +1,40 @@ +/* -*- C++ -*- */ +/* + * Copyright 2010 Free Software Foundation, Inc. + * + * This file is part of GNU Radio + * + * GNU Radio is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3, or (at your option) + * any later version. + * + * GNU Radio is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +%rename(cpm) gr_cpm; + +class gr_cpm +{ + public: + enum cpm_type { + LRC, + LSRC, + LREC, + TFM, + GAUSSIAN, + GENERIC = 999 + }; + + static std::vector<float> + phase_response(cpm_type type, unsigned samples_per_sym, unsigned L, double beta=0.3); +}; + diff --git a/gnuradio-core/src/lib/general/qa_general.cc b/gnuradio-core/src/lib/general/qa_general.cc index 6984d798c..b9080f362 100644 --- a/gnuradio-core/src/lib/general/qa_general.cc +++ b/gnuradio-core/src/lib/general/qa_general.cc @@ -28,6 +28,7 @@ #include <qa_general.h> #include <qa_gr_firdes.h> #include <qa_gr_circular_file.h> +#include <qa_gr_cpm.h> #include <qa_gr_fxpt.h> #include <qa_gr_fxpt_nco.h> #include <qa_gr_fxpt_vco.h> @@ -41,6 +42,7 @@ qa_general::suite () s->addTest (qa_gr_firdes::suite ()); s->addTest (qa_gr_circular_file::suite ()); + s->addTest (qa_gr_cpm::suite ()); s->addTest (qa_gr_fxpt::suite ()); s->addTest (qa_gr_fxpt_nco::suite ()); s->addTest (qa_gr_fxpt_vco::suite ()); diff --git a/gnuradio-core/src/lib/general/qa_gr_cpm.cc b/gnuradio-core/src/lib/general/qa_gr_cpm.cc new file mode 100644 index 000000000..cc32d1117 --- /dev/null +++ b/gnuradio-core/src/lib/general/qa_gr_cpm.cc @@ -0,0 +1,140 @@ +/* -*- c++ -*- */ +/* + * Copyright 2010 Free Software Foundation, Inc. + * + * This file is part of GNU Radio + * + * GNU Radio is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3, or (at your option) + * any later version. + * + * GNU Radio is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +#include <qa_gr_cpm.h> +#include <gr_cpm.h> +#include <cppunit/TestAssert.h> + +const double DELTA = 1e-5; +const int L = 5; +const int samples_per_sym = 4; +const float taps_lrc[20] = { + 0, 0.002447174185242, 0.009549150281253, 0.020610737385376, + 0.034549150281253, 0.050000000000000, 0.065450849718747, 0.079389262614624, + 0.090450849718747, 0.097552825814758, 0.100000000000000, 0.097552825814758, + 0.090450849718747, 0.079389262614624, 0.065450849718747, 0.050000000000000, + 0.034549150281253, 0.020610737385376, 0.009549150281253, 0.002447174185242 +}; + + +const float taps_lsrc[20] = { // beta = 0.2 + 0.000000000000000, 0.009062686687436, 0.019517618142920, 0.030875041875917, + 0.042552315421249, 0.053912556756416, 0.064308860403517, 0.073130584159352, + 0.079847961304114, 0.084051371489937, 0.085482007518284, 0.084051371489937, + 0.079847961304114, 0.073130584159352, 0.064308860403517, 0.053912556756416, + 0.042552315421249, 0.030875041875917, 0.019517618142920, 0.009062686687436 +}; + + +const float taps_tfm[20] = { + -0.003946522220317, -0.005147757690530, -0.003171631690177, 0.003959659609805, + 0.017498721302356, 0.037346982678383, 0.062251889790391, 0.087364237065604, + 0.110049050955117, 0.125677762224511, 0.132288693729399, 0.125677762224511, + 0.110049050955117, 0.087364237065604, 0.062251889790391, 0.037346982678383, + 0.017498721302356, 0.003959659609805, -0.003171631690177, -0.005147757690530 +}; + + +const float taps_gaussian[20] = { // BT = 0.3 + 0.000000743866524, 0.000009286258371, 0.000085441834550, 0.000581664421923, + 0.002945540765422, 0.011178079812344, 0.032117220937421, 0.070841188736816, + 0.122053715366673, 0.167389736919915, 0.185594670675172, 0.167389736919915, + 0.122053715366673, 0.070841188736816, 0.032117220937421, 0.011178079812344, + 0.002945540765422, 0.000581664421923, 0.000085441834550, 0.000009286258371 +}; + + +// Check LREC phase response +void +qa_gr_cpm::t1 () +{ + std::vector<float> taps(gr_cpm::phase_response(gr_cpm::LREC, samples_per_sym, L)); + + for (int i = 0; i < L * samples_per_sym; i++) { + CPPUNIT_ASSERT_DOUBLES_EQUAL(taps[i], 0.05, DELTA); + } +} + + +// Check LRC phase response +void +qa_gr_cpm::t2 () +{ + std::vector<float> taps(gr_cpm::phase_response(gr_cpm::LRC, samples_per_sym, L)); + float sum = 0; + + for (int i = 0; i < L * samples_per_sym; i++) { + CPPUNIT_ASSERT_DOUBLES_EQUAL(taps[i], taps_lrc[i], DELTA); + sum += taps[i]; + } + + CPPUNIT_ASSERT_DOUBLES_EQUAL(sum, 1.0, DELTA); +} + + +// Check LSRC phase response +void +qa_gr_cpm::t3 () +{ + std::vector<float> taps(gr_cpm::phase_response(gr_cpm::LSRC, samples_per_sym, L, 0.2)); + float sum = 0; + + for (int i = 0; i < L * samples_per_sym; i++) { + CPPUNIT_ASSERT_DOUBLES_EQUAL(taps[i], taps_lsrc[i], DELTA); + sum += taps[i]; + } + + CPPUNIT_ASSERT_DOUBLES_EQUAL(sum, 1.0, DELTA); +} + + +// Check the TFM phase response +void +qa_gr_cpm::t4 () +{ + std::vector<float> taps(gr_cpm::phase_response(gr_cpm::TFM, samples_per_sym, L)); + float sum = 0; + + for (int i = 0; i < L * samples_per_sym; i++) { + CPPUNIT_ASSERT_DOUBLES_EQUAL(taps[i], taps_tfm[i], DELTA); + sum += taps[i]; + } + + CPPUNIT_ASSERT_DOUBLES_EQUAL(sum, 1.0, DELTA); +} + + +// Check the Gaussian phase response +void +qa_gr_cpm::t5 () +{ + std::vector<float> taps(gr_cpm::phase_response(gr_cpm::GAUSSIAN, samples_per_sym, L, 0.3)); + float sum = 0; + + for (int i = 0; i < L * samples_per_sym; i++) { + CPPUNIT_ASSERT_DOUBLES_EQUAL(taps[i], taps_gaussian[i], DELTA); + sum += taps[i]; + } + + CPPUNIT_ASSERT_DOUBLES_EQUAL(sum, 1.0, DELTA); +} + diff --git a/gnuradio-core/src/lib/general/qa_gr_cpm.h b/gnuradio-core/src/lib/general/qa_gr_cpm.h new file mode 100644 index 000000000..741cb2860 --- /dev/null +++ b/gnuradio-core/src/lib/general/qa_gr_cpm.h @@ -0,0 +1,49 @@ +/* -*- c++ -*- */ +/* + * Copyright 2010 Free Software Foundation, Inc. + * + * This file is part of GNU Radio + * + * GNU Radio is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3, or (at your option) + * any later version. + * + * GNU Radio is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ +#ifndef _QA_GR_CPM_H +#define _QA_GR_CPM_H + +#include <cppunit/extensions/HelperMacros.h> +#include <cppunit/TestCase.h> + +class qa_gr_cpm : public CppUnit::TestCase { + + CPPUNIT_TEST_SUITE (qa_gr_cpm); + CPPUNIT_TEST (t1); + CPPUNIT_TEST (t2); + CPPUNIT_TEST (t3); + CPPUNIT_TEST (t4); + CPPUNIT_TEST (t5); + CPPUNIT_TEST_SUITE_END (); + + private: + void t1 (); + void t2 (); + void t3 (); + void t4 (); + void t5 (); + +}; + + +#endif /* _QA_GR_CPM_H */ + |